1. Field of the Invention
The present invention generally relates to methods for repairing components subjected deformation as a result of high temperature creep, such as turbine blades of gas turbine engines. More particularly, this invention relates to a method of repairing a gas turbine engine blade whose platform has become bowed as a result of high temperature creep.
2. Description of the Related Art
High temperature nickel-base superalloys are widely used in the manufacture of components for the high temperature sections of gas turbine engines. Such components, which include nozzles, combustors, and turbine vanes and blades, are under strenuous high temperature conditions during engine operation that can lead to various types of damage or deterioration. Because the material and processing costs of superalloys are relatively high, restoration and repair of damaged or worn superalloy components are typically preferred to replacement. For this purpose, various weld repair methods have been developed, including those using tungsten inert gas (TIG) and plasma transferred arc (PTA) welding processes performed at room and elevated temperatures to improve welding yields and ensure that the mechanical properties of the superalloy are maintained. Particularly suitable welding processes, referred to as superalloy welding at elevated temperatures (SWET), are disclosed in U.S. Pat. Nos. 6,020,511, 6,124,568 and 6,297,474. SWET welding processes are performed within an enclosure in which a controlled atmosphere and temperature are maintained to inhibit cracking and oxidation of a superalloy component being repaired.
A particular example of damage that can occur is the result of high temperature creep to which rotating gas turbine components are susceptible. Platforms of gas turbine engine blades can become bowed as a result of high temperature creep, necessitating scrappage of the blade if the bow is excessive. In view of the high material and processing costs of turbine blades, it would be desirable if blades that have sustained excessive platform bow could be repaired and restored to extend their service life.